<!DOCTYPE html>
<html lang="en">

  <head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>relative练习一</title>
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  <style>
    sub {
      position: relative;
      top: 10px;
      left: 10px;
    }

    sup {
      position: relative;
      top: -20px;
      left: 20px;
    }
  </style>

  <body>
    <h1>请计算n<sub>1</sub>+n<sub>2</sub>+n<sup>2</sup>的值</h1>
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